How to modify vanilla items using mixin? | The Fabric Project | Page 1

past citrus Jul 28, 2025, 2:57 PM

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I want to modify some attributes and components of vanilla tools and weapons. How am I suppose to do that with mixin? I'm like 1 week into modding and I know very little

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This is my code currently

@Mixin(Items.class)
public abstract class ItemsMixin {

    @Shadow
    public static final Item GOLDEN_SWORD = register("golden_sword", new Item.Settings().sword(ToolMaterial.GOLD, 5.0F, -2.4F));

}

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1.21.8 btw

safe cave Jul 28, 2025, 3:16 PM

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not sure if you actually can change static final variables

golden galleon Jul 28, 2025, 3:20 PM

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The Shadow annotation does not allow you to change the definition* of a var. It only lets you use it

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I'd suggest using a @Inject injecting into the register method

past citrus Jul 29, 2025, 3:50 AM

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uhmm this does not work

public abstract class ItemsMixin {
    @Shadow
    public static Item GOLDEN_SWORD;

    @Inject(method = "<clinit>", at = @At("TAIL"))
    public static void ModifyGoldenSword(CallbackInfo ci) {
        GOLDEN_SWORD = new Item.Settings().sword(ToolMaterial.GOLD, 5.0F, -2.4F);
    }
}

did I do anything wrong?

Edit: Added ModifyGoldenSword between void and (CallbackInfo ci), still not working

past citrus Jul 29, 2025, 3:53 AM

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past citrus This is my code currently ``` @Mixin(Items.class) public abstract class ItemsMix...

I did something similar to this to modify ToolMaterial and it worked, but it doesn't work with Items

left python Jul 29, 2025, 4:48 AM

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no, this is not good

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don't reinitialize the item, this will override anything other mods would add.

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you should do precise changes, in this case only to the item settings

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that way for example if someone makes a sword edible, that wouldn't be lost

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it will have both settings

past citrus Jul 29, 2025, 1:52 PM

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uhmmm

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howd you do that?

left python Jul 29, 2025, 2:01 PM

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use a @Slice to narrow down the search scope, generally you can easily target a constant value like "golden_sword"
use a injector that lets you do precise changes: ModifyExpressionValue, ModifyArg

past citrus Jul 30, 2025, 8:38 AM

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can you provide some examples, because I'm still a beginner and those wiki pages don't make much sense to me?

unborn narwhal Jul 30, 2025, 8:56 AM

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why not just use the default item component event from fapi

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you can use an accessor on ComponentMap$Builder to access its components which would let you modify them instead of overwriting (if needed)

left python Jul 30, 2025, 12:08 PM

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does it let you modify the tool material?

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or is that not needed in OP's case?

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wait tool material is a part of the component

past citrus Jul 30, 2025, 2:16 PM

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yes it did

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all I did was

@Mixin(ToolMaterial.class)
public abstract class ToolMaterialMixin {

    @Shadow
    public static final ToolMaterial GOLD = new ToolMaterial(BlockTags.INCORRECT_FOR_GOLD_TOOL, 984, 8.0F, 0.0F, 22, ItemTags.GOLD_TOOL_MATERIALS);
    
}

and it worked perfectly fine

warm steeple Jul 31, 2025, 1:34 AM

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golden galleon The `Shadow` annotation does not allow you to change the definition* of a var. I...

It technically lets you reassign to it also, as shadow initializers / assignments are merged

golden galleon Jul 31, 2025, 1:45 AM

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But it should never be used like that, so I pretend it doesn't work tiny_potato

warm steeple Jul 31, 2025, 1:52 AM

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golden galleon But it should never be used like that, so I pretend it doesn't work <:tiny_potat...

Wdym?

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It's quite common to do and actually quite useful

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Saves an injector

golden galleon Jul 31, 2025, 1:52 AM

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but it's not stackable

warm steeple Jul 31, 2025, 2:26 AM

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golden galleon but it's not stackable

I mean, it depends on what you want to stack

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If you use the original value it stacks just fine

past citrus Jul 31, 2025, 8:39 AM

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past citrus all I did was ``` @Mixin(ToolMaterial.class) public abstract class ToolMaterial...

I did this for ToolMaterial and it worked

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but when I used similar code for Items

@Mixin(Items.class)
public abstract class ItemsMixin {

    @Shadow
    public static final Item GOLDEN_SWORD = register("golden_sword", new Item.Settings().sword(ToolMaterial.GOLD, 5.0F, -2.4F));

}

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it didn't work

unborn narwhal Jul 31, 2025, 8:54 AM

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unborn narwhal why not just use the default item component event from fapi

.

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or mixin into the register method

past citrus Jul 31, 2025, 8:55 AM

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unborn narwhal or mixin into the register method

which method?

unborn narwhal Jul 31, 2025, 8:56 AM

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Items.register

past citrus Jul 31, 2025, 9:07 AM

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@Mixin(Items.class)
public abstract class ItemMixin {

    @Shadow
    public static final Item GOLDEN_SWORD = Items.register("golden_sword", new Item.Settings().sword(ToolMaterial.GOLD, 9.0F, 4F));

}

still crashing

unborn narwhal Jul 31, 2025, 9:08 AM

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well thats not doing what I said

past citrus Jul 31, 2025, 9:10 AM

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so how would you do it?

unborn narwhal Jul 31, 2025, 9:13 AM

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either doing what diced said, or modifying the args passed to the other overload in the String, Item$Settings overload (which is less compatible with other injectors mixing into the same overload)

past citrus Jul 31, 2025, 9:16 AM

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I tried to read the wiki he sent and it just went over my head

#How to modify vanilla items using mixin?